Transimpedance amplifier for receiving burst optical signal

1. A transimpedance amplifier configured to convert an input current generated by a photodetector in accordance with a burst optical signal to a differential signal including a positive-phase component and a negative-phase component and output the differential signal, the transimpedance amplifier comprising:

a single-ended amplifier configured to convert a current signal to a voltage signal;

an amplifier circuit configured to generate a reference voltage signal;

a first feedback circuit having a time constant, the first feedback circuit being configured to generate a bypass current at a response speed adjusted by the time constant;

a differential amplifier circuit configured to generate the differential signal in accordance with a difference between the voltage signal and the reference voltage signal; and

a detector circuit configured to detect a start and an end of the burst optical signal based on the differential signal, wherein

the first feedback circuit generates the bypass current in accordance with the difference between the voltage signal and the reference voltage signal and generates the current signal by subtracting the bypass current from the input current, and

the detector circuit detects the end of the burst optical signal based on a first peak value of the positive-phase component and a second peak value of the negative-phase component and switches the time constant of the first feedback circuit from a first time constant to a second time constant smaller than the first time constant for a predetermined period in response to detecting the end of the burst optical signal.

2. The transimpedance amplifier according to claim 1 , wherein

the detector circuit includes a single-phase peak-hold circuit configured to detect the second peak value and a first threshold generator circuit configured to generate a first threshold in accordance with the first peak value, and

the detector circuit detects the end of the burst optical signal upon detecting that the second peak value is larger than the first threshold.

3. The transimpedance amplifier according to claim 1 , wherein the detector circuit detects the start of the burst optical signal based on a third peak value of the differential signal and a mean value of the differential signal and switches the time constant of the first feedback circuit from the first time constant to the second time constant for the predetermined period in response to detecting the start of the burst optical signal.

4. The transimpedance amplifier according to claim 3 , wherein

the detector circuit includes a differential peak-hold circuit configured to detect the third peak value and a second threshold generator circuit configured to generate a second threshold in accordance with the mean value, and

the detector circuit detects the start of the burst optical signal upon detecting that the third peak value is larger than the second threshold.

5. The transimpedance amplifier according to claim 1 , wherein

the burst optical signal includes a preamble signal and a payload signal following the preamble signal, and

the predetermined period is shorter than a period of the preamble signal.

6. The transimpedance amplifier according to claim 1 , further comprising a second feedback circuit configured to control the differential amplifier circuit in accordance with feedback of both the positive-phase component and the negative-phase component to remove a DC offset in the differential signal.

7. A transimpedance amplifier configured to convert an input current generated by a photodetector in accordance with a burst optical signal to a differential signal including a positive-phase component and a negative-phase component and output the differential signal, the transimpedance amplifier comprising:

a single-ended amplifier configured to convert a current signal to a voltage signal;

an amplifier circuit configured to generate a reference voltage signal;

a first feedback circuit including a capacitor, the first feedback circuit being configured to generate a bypass current in accordance with a charging voltage of the capacitor based on a difference between the voltage signal and the reference voltage signal;

a differential amplifier circuit configured to generate the differential signal in accordance with the difference between the voltage signal and the reference voltage signal; and

a detector circuit configured to detect a start and an end of the burst optical signal based on the differential signal, wherein

the first feedback circuit generates the current signal by subtracting the bypass current from the input current, and

the detector circuit detects the end of the burst optical signal based on a first peak value of the positive-phase component and a second peak value of the negative-phase component and releases electric charge stored in the capacitor to reset the charging voltage in response to detecting the end of the burst optical signal.

8. The transimpedance amplifier according to claim 7 , wherein

the detector circuit includes a single-phase peak-hold circuit configured to detect the second peak value and a first threshold generator circuit configured to generate a first threshold in accordance with the first peak value, and

the detector circuit detects the end of the burst optical signal upon detecting that the second peak value is larger than the first threshold.

9. The transimpedance amplifier according to claim 7 , wherein the detector circuit detects the start of the burst optical signal based on a third peak value of the differential signal and a mean value of the differential signal and switches a time constant of the first feedback circuit from a first time constant to a second time constant smaller than the first time constant for a predetermined period in response to detecting the start of the burst optical signal.

10. The transimpedance amplifier according to claim 9 , wherein

the detector circuit includes a differential peak-hold circuit configured to detect the third peak value and a second threshold generator circuit configured to generate a second threshold in accordance with the mean value, and

the detector circuit detects the start of the burst optical signal upon detecting that the third peak value is larger than the second threshold.

11. The transimpedance amplifier according to claim 9 , wherein

the burst optical signal includes a preamble signal and a payload signal following the preamble signal, and

the predetermined period is shorter than a period of the preamble signal.

12. The transimpedance amplifier according to claim 7 , further comprising a second feedback circuit configured to control the differential amplifier circuit in accordance with feedback of both the positive-phase component and the negative-phase component to remove a DC offset in the differential signal.

13. The transimpedance amplifier according to claim 1 , wherein

the amplifier circuit configured to generate a reference voltage signal is a dummy amplifier, and

the reference voltage signal has the value of the voltage signal output from the single-ended amplifier when the input current is zero.

14. The transimpedance amplifier according to claim 7 , wherein

the amplifier circuit configured to generate a reference voltage signal is a dummy amplifier, and

the reference voltage signal has the value of the voltage signal output from the single-ended amplifier when the input current is zero.